This invention relates to curable oxirane polymers comprising an addition polymer backbone bearing pendant oxirane groups.
Coatings based on epoxy resins, i.e., those derived from oxirane polymers, provide good solvent resistance, hardness, adhesion and the like and are therefore widely used as coatings for a wide variety of substrates such as metal, wood, plastic and the like. Unfortunately, however, such coatings are noted for their tendency to yellow and chalk when exposed to ultraviolet light and other weathering conditions.
This yellowing tendency is particularly evident when aromatics, such as bisphenol A, are employed as monomeric components of the resin and/or when amines, such as diethylenetriamine and the like, are used as curing agents. Accordingly, epoxy resin compositions, wherein the problems of yellowing, chalking and other deterioration caused by exposure to light are minimized, have been pursued by the coating industries for a substantial period of time.
In view of the aforementioned deficiencies of conventional epoxy resin compositions and the desire of the coating industries to employ epoxy resin compositions free from such deficiencies, it is highly desirable to provide a hard, adhesive, solvent-resistant coating derived from an oxirane polymer which coating exhibits increased resistance to degradation upon exposure to ultraviolet light and other conditions common to the environment.